1. Technical Field
This invention relates to hydraulic food cutting apparatus and more particularly to a hydraulic food cutter having a pressure sensitive control system and a plurality of automatically interchangeable cutter blade assemblies.
2. Background Art
Many food products, particularly vegetables and fruits are processed prior to sale either by canning or freezing. Unless the product involved is of a naturally occurring edible size, for example peas, the product is usually trimmed and sliced, or diced, to edible size prior to preservation processing such as canning or freezing.
The slicing, dicing and other cutting operations have traditionally been accomplished with mechanical cutters. However, relatively recent advances in food product cutting technologies have resulted in the common use of hydraulic cutting apparatus which can be used to cut food products at relatively high speeds. Cutting capacities of 20,000 pounds to 35,000 pounds per hour are not unusual.
Hydraulic food cutters are used to cut a wide variety of food products, including potatoes, beets, zucchini or cucumbers, amongst others. The prior art relevant to the present invention are the food cutting devices themselves, and not the food product being cut. However, to place the present invention in proper context, and for purposes of clear illustration, this specification presents the prior art and the preferred embodiment in the context of a food cutter cutting potatoes. Cutting potatoes has been the most common application of the present machine. However, it should be distinctly understood that these hydraulic food cutters are capable of cutting and are used to cut a wide variety of food products.
In a typical prior art hydraulic cutting apparatus, where potatoes are to be cut, the potatoes are dropped into a tank filled with water and then pumped through conduit into an alignment chute or tube wherein the potatoes are aligned and accelerated to high speed before impinging upon a fixed array of cutter blades where the potato is cut into a plurality of smaller pieces.
The basic configuration of a prior art system, with the present invention added in, is shown in schematic format, in FIG. 16. One of the main components of a prior art hydraulic cutting apparatus for use in cutting potatoes is a receiving tank into which peeled or unpeeled potatoes are dropped. A food pump, usually a single impeller centrifugal pump, is provided. It draws its suction from the receiving tank and pumps water and the suspended potatoes from the tank into an accelerating tube which functions as the converging portion of a venturi. The accelerator tube is used to accelerate and align the potatoes immediately prior to impinging upon the stationary knife blades of the cutter blade assembly.
Each whole potato impinging upon the knife blade assembly passes through the cutting blade array and is thereby cut into a plurality of food pieces, for example french fry pieces, which pass with the water into the second half of the venturi which is a diverging tube in which the water and the cut food pieces are decelerated back to a slower velocity. The water and cut food pieces are then deposited onto a dewatering conveyer chain. The water passes through the dewatering conveyor chain and is collected and recycled back to the receiving tank. The cut food pieces remain on the conveyor chain and are carried off for further processing. In the past, significant effort has been directed toward the development of good alignment or acceleration tubes which can properly align and accelerate the whole food product so that each whole food product is properly centered relative to the cutter blade array prior to impinging upon it. Additional efforts have been made to develop cutter blade arrays or head assemblies that can be used to cut whole food product without plugging. Examples of these efforts can be seen in my patents, U.S. Pat. Nos. 5,095,794, and 5,125,308, which disclose designs for cutter blade arrays. U.S. Pat. No. 4,614,141 teaches an alignment tube assembly which is used to accelerate and align whole potatoes immediately prior to impinging upon a cutter head array. The teachings of U.S. Pat. Nos. 5,095,794, 5,125,308 and 4,614,141 are hereby incorporated by reference.
The problem is that, despite efforts to develop good alignment or acceleration tubes and cutter blade assemblies, virtually all hydraulic cutters will still occasionally plug. The exact mechanism by which a potato plugs or fails to pass cleanly through a cutter blade assembly involves the study of hydrodynamics, and statics and dynamics as they relate to the cellular structure of food products. As a result, the exact mechanism by which the cutter head plugs is not known, all that is known is that, despite all recent efforts, occasionally a food product, such as a potato, will not pass completely through the cutter head assembly, either leaving behind portions of cut food product and/or portions of uncut food product.
What happens when a food product does not pass completely through the cutter blade assembly is that the machine rapidly plugs up. For potatoes, at a 20,000 pound per hour cutting rate, given an average 10 ounce potato, the number of potatoes passing through the cutter blade assembly is approximately 32,000 potatoes per hour, or approximately 8.8 potatoes per second. If one potato plugs the cutter blade assembly, in 10 seconds there will be 88 potatoes backed up behind the cutter blade assembly; in 20 seconds, 176 potatoes. At 35,000 pounds per hour the problem is further aggravated. In practice, if a prior art hydraulic cutting apparatus plugs while unattended, it is not uncommon for the plug to include backed up, smashed potatoes all the way back and into the food pump. A plug such as this can take hours to clean out since it requires substantial disassembly of the machine and its attendant piping. As a result, it is common practice in food processing plants to provide operating personnel to continuously monitor the operation of the hydro-cutting system.
The study of what actually happens on a microscopic or cellular level when a food product, such as a potato, impinges upon the cutting blades of a cutter blade assembly is actually the study of hydrodynamics interplaying with the physics of the tearing and breaking of organic cellular structure. As a result, the actual dynamics of the cutting cannot be accurately and completely mathematically modeled. Design of cutter blade assemblies and the establishment of cutter parameters, such as fluid flow, volumes and rates for food product feed, are generally empirically determined. One thing is known, however, and that is that the sharper the cutting edges of the cutting blades, the better the quality of the cut food pieces being produced by the hydraulic food cutter. For this reason it is common practice in the industry to replace the cutter blade assembly after every three to four hours of use with a new cutter blade assembly having resharpened or replaced cutter blades. In general, a three or four hour replacement schedule is commonly used in the potato processing industry and is a compromise between food product quality and production efficiency. Replacement of the blades more frequently would produce a higher quality product. However, in the prior art, replacement of the blade holder assembly required shutting down the system for a significant period of time, and as a result the three or four hour changeover rule has been generally followed. The present invention provides a means whereby cutter heads can be replaced on a much more frequent basis than that generally available to prior art systems.
Accordingly, it is an object of the present invention to provide an apparatus which quickly senses the presence of the failure of a food product to pass completely through the cutter blade array so that the machine can either shut down, or, alternatively, automatically replace the cutter blade array assembly which is plugging with an unplugged, or clean, cutter head assembly.
Another object of the present invention is to provide a hydro-cutter assembly which has a mechanism whereby the cutter head assembly can be quickly removed from the line of fluid flow so that a mass of plugging food product can be flushed through the system thus eliminating the need to shut the entire system down for manual removal of a plugging mass of food product.
A third object of the present invention is to provide a hydro-cutting assembly which has the capability of either periodically, or selectively, changing cutter blade arrays so as to ensure that dull cutter blade knives are replaced prior to deterioration of the quality of the cut food product being processed.